Orthodontic arch wire and method of forming the same

ABSTRACT

An orthodontic arch wire and a method of forming the same are disclosed, the method including the steps of coiling a single flexible metallic strand to form a tightly wound helix normally having an array of successively abutting and substantially parallel turns. The helix is made from a material sufficiently flexible to permit bending of the arch wire by selectively and at least partially separating adjacent turns of the helix. According to one presently preferred embodiment, the adjacent turns each lie in a respective plane extending substantially transversely to the longitudinal axis of the helix.

United States Patent Wallshein [451 Jan. 21, 1975 ORTHODONTIC ARCH WIRE AND METHOD OF FORMING THE SAME [76] Inventor: Melvin Wallshein, 8645 Bay Pky.,

Brooklyn, NY. 11214 [22] Filed: Oct. 25, 1972 [21] Appl. No.: 300,444

[52] US. Cl 32/14 A [51] Int. Cl A6lc 7/00 [58] Field of Search 32/14 A [56] References Cited UNITED STATES PATENTS 3,052,081 9/1962 Wallshein 32/14 A 3,593,421 7/1971 Brader 32/14 A Primdry ExaminerRobert Peshock Attorney, Agent, or Firm-Friedman & Goodman [57] ABSTRACT An orthodontic arch wire and a method of forming the same are disclosed, the method including the steps of coiling a single flexible metallic strand to form a tightly wound helix normally having an array of successively abutting and substantially parallel turns. The helix is made from a material sufficiently flexible to permit bending of the arch wire by selectively and at least partially separating adjacent turns of the helix. According to one presently preferred embodiment, the adjacent turns each lie in a respective plane extending substantially transversely to the longitudinal axis of the helix.

1 Claim, 8 Drawing Figures ORTHODONTIC ARCH WIRE AND METHOD OF FORMING THE SAME BACKGROUND OF THE INVENTION The present invention generally relates to orthodontic arch wires, and more particularly to an arch wire constituted of a single metallic strand in the form of a tightly wound helix, and a method of forming the same.

The following definitions apply to the specification and claims. Stiffness is the resistance of a material to bending or deformation. Flexibility" is the ability of a material to bend or deform. Plastic deformation is a permanent change in the shape of a material. Once plastic deformation takes place, the removal of forces which caused the change in shape does not result in a return of the material to its original shape. The elastic limit of a material is the maximum load or deformation which can be applied to a material before plastic or permanent deformation takes place. Resiliency is the tendency of a flexed material to spring back to its original configuration on the removal of the flexing forces. Working Range is the range of deformation of a material where it retains its resiliency, up to maximum deformation which can be sustanined by a material without exceeding the elastic limit and becoming permanently deformed with loss of resiliency.

Orthodontic procedures usually require the placement of a tooth band and bracket upon respective maloccluded teeth and the employment of an arch wire for interconnecting the bands or brackets relative to one another so that a force is transmitted from one band to the next and thereby to the teeth upon which the bands are mounted. Today, the orthodontist is offered a wide variety of arch wires. The known arch wires vary both in size and material. An ideal arch wire must be flexible, but must have sufficient stiffness or body over long lengths so that it can serve as a relatively fixed anchoring or reference point to which other orthodontic devices can be connected. The flexibility, of course, is required so that the arch wire can be bent into the shape of an arch in the mouth. It is also desirable that the arch wire have a resiliency and sufficient range over short and long lengths in order to permit the application of local biasing forces to the teeth. Most wires do have the quality of resiliency over limited ranges of bending or deformation these wires becoming permanently deformed and losing all resiliency once the wire is bent beyond its elastic limit. In other words, these wires have a limited working range, as defined above.

The known arch wires do not provide the required combination of characteristics which an ideal arch wire should possess. Thus, while most known arch wires are flexible and provide the requisite stiffness over long lengths, these wires have a limited working range over short lengths. In order to apply local stresses to one or more teeth, it is frequently necessary to provide individual areas along the arch wire which have a high degree of resiliency. Since known arch wires with their limited working ranges cannot normally provide this high degree of springiness or resiliency by mere bending the normal method of activating the restoring forces it has been the common practice to make large loops from the arch wire. By making large loops, the arch wire is not drastically bent in a short length, but rather is curved over a longer length of the large loop. In this manner, the elastic limit of the wire is not exceeded at any one point and the wire reteains its resiliency.

The solid wire, which is the most common type used, exhibits the requisite flexibility and stiffness over long lengths. However, a generally long length of the solid wire is required to obtain any meaningful amount of flexing without permanently deforming the wire. In a small space of approximately three millimeters solid wire is practically rigid, does not have the requisite working range; and if the wire is bent in such a small space, it is permanently deformed and does not tend to spring back to its initial configuration.

In order to increase the working range of a wire in a small space, solid wires have been replaced in some instances by multiple-wire arrangements in which a plurality of thin wires are combined to provide an effective cross-sectional area which is substantially equal to the original cross-sectional area of the solid wire. The multiple arch wire is more flexible than the solid wire of comparable cross-section. The working range, however, of the multiple-wire arrangement is greater than the solid wire counterpart. The multiple-wire still has sufficient stiffness or body, although this is less than the solid wire. Despite the desirable increase in working range, the muliple arch wire has other disadvantages which have limited its use. For example, the ends of the multiple-wires have formed impaling or piercing devices upon the tissues in the mouth. The ends of the multiple arch wires spread out in time and impair the sensitive tissues in the mouth. Also, the thinner individual strands are relatively weak and subject to rupture. Generally, the strands do not rupture as a unit, but each strand ruptures under the pressure of the bite or something abrassive in the mouth. Thus, the multiple arch wire has a weakness which makes it unable to hold up to stresses in the mouth. To aggravate the problem, rupture of the individual strands causes the ruptured free ends to spread out in time and mutilated sensitive tissues of the mouth.

A further attempt in the evolution of arch wires to obtain the combined characteristics of flexibility, stiffness over long lengths, resiliency and an increased working range in short lengths has been the development of arch wires formed from multiple strands which are twisted together in the form of a rope. This twisted arch wire is more flexible than a corresponding solid arch wire of comparable cross-section since the flexibility of the twisted wire is related to the greater flexibility of the individual minor strands. Thus, although the overall cross-sectional areas of both the solid wire and the twisted wires may be approximately equal, the flexibility of the twisted arch wire is substantially greater than that of the solid wire. Over short lengths, however, the twisted wire has a greater working range than a solid wire and can be bent to a greater extent without being permanently deformed and loosing its resiliency. The twisted wire, being made from a plurality of thinner and weaker wires, as in the multiple-wire arrangement, has the same disadvantages as the latter. However, tightly wound multiple wires have had a lesser tendency to open up and fray than the above described multiple-wire arrangement.

Also, there is known in the prior art, a solid arch wire which includes a plurality of spaced helical convolutions which can be either openly or closely wound. However, the convolutions form only a relatively small portion of the overall arch wire length and are provided as coils spaced on a solid arch wire instead of being a coil forming the entire length of the arch wire as the basic configuration of the arch wire. With this known arch wire, in the case of the open convolutions, the required stiffness over long lengths is lost. The provision of spaced closed convolutions only along sections of the arch wire decreases the versatility at which bends may be made in the arch wire. Thus, the last described arch wire basically consists of a solid arch wire with spaced coils thereon.

SUMMARY OF THE INVENTION To overcome the above disadvantages, it is an object of the present invention to provide an orthodontic arch wire and method of forming the same which isnot possessed of the prior art'disadvantages.

It is another object of the present invention to provide an orthodontic arch wire of the type under discussion, and method of forming the same, which is simple in construction and economical to manufacture.

It is still another object of the present invention to provide an orthodontic arch wire of the type under discussion which provides the requisite stiffness or body over relatively long lengths.

It is a further object of the present invention to provide an orthodontic arch wire of the type under discussion which can obviate most loops and other orthodontic arch configurations and still provide localized areas of resiliency in small spaces.

It is yet a further object of the present invention to provide an arch wire as above described which exhibits the requisite flexibility over long lengths and has a considerable working range over short lengths.

To achieve the above, as well as other objects which will become obvious hereafter, the orthodontic arch wire in accordance with the present invention comprises a single twisted strand in the form of a tightly wound helix normally having an array of successively abutting and substantially parallel turns. The helix is made from material sufficiently elastic to permit bending of the arch wire by selectively and at least partially separating adjacent turns.

According to one presently preferred embodiment, the orthodontic wire deifnes an axis and each of the turns of the helix lies in a respective plane substantially normal to the axis. The strand may have either a square or round cross-section and is preferably made from a metal.

According to an important feature of the invention, the arch wire helix has an inner diameter which is equal to no more than twice the diameter or thickness of the individual strand as measured in the radial direction of the helix. According to another feature of the present invention, the helix has an elongated axial passage or lumen through the turns. A resilient mandrel extends through the passage. According to still a further feature, a resilient coating made from a platicized or elastomeric material is provided exteriorly and along said helix for enclosing the same. The single strand may have a circular or rectangular cross-section.

The method of forming the above orthodontic arch wire cmprises the step of coiling a single flexible strand into a tightly-wound helix having an array of successively abutting and substantially parallel turns.

Basically, the improvement in accordance with the present invention involves forming an arch wire which has greater range than a solid wire over short lengths.

Thus, the subject wire can be bent over short lengths to provide localized areas of resiliency. This obviates, in many cases, the need for loops conventionally used with prior art solid wires. However, the new wire does not sacrifice to any great degree the stiffness required of arch wires over longer lengths. This is achieved by coiling a particular sized wire into a helix having an outer diameter substantially equal to those of commonly used arch wires. The wire is coiled so tight that it looses some of the characteristics inherent in extremely flexible pure coils which have little stiffness over long lengths. The present wire exhibits characteristics which are substantially intermediate to those of a solid wire and to those of a pure coil in that the wire has more flexibility than the solid wire but more stiffness than the pure coil over long lengths. By tightly winding the coils so that adjacent turns of the helix abut against one another, sufficient stiffness is given to the wire over long lengths while giving it the increased range over small lengths such as three or four milimeters. Thus, contrary to solid wires, the present wire is sufficiently resilient so as to spring back subsequent to flexing over the short lengths. It has been found that requisite stiffness cannot be obtained with a pure or open coil but only with a very tightly wound coil as described herein.

BRIEF DESCRIPTION OF THE DRAWINGS With the above and additional objects and advantages in view as will hereinafter appear, this invention comprises the devices, combinations and arrangements of parts hereinafter described and illustrated in the accompanying drawings of a preferred embodiment in which:

FIG. 1 is a front view of the orthodontic arch wire pursuant to one embodiment of the present invention;

FIG. 2 is a cross-sectional view taken along the line 22 in FIG. 1;

FIG. 3 is an enlarged fragmented perspective view of an orthodontic bracket in association with the orthodontic arch wire pursuant to the embodiment illustrated in FIG. 1;

FIG. 4 is a view similar to that of FIG. 2, showing plasticized or elastomeric on the exterior of the wire;

FIG. 5 is an enlarged front elevational view of adjacent orthodontic brackets as mounted on respective teeth (not shown) and, as associated with a common orthodontic arch wire pursuant to the embodiment illustrated in FIG. 1',

FIG. 6 is a view, similar to that, of FIG. I of an alternate embodiment of the present invention which uses a strand having a rectangular cross-section;

FIG. 7 is a cross-sectional view taken along line 5-5 in FIG. 6; and

FIG. 8 is a view similar to that of FIG. 6, showing an orthodontic construction of the second embodiment wherein the turns are inclined at a steeper angle with respect to the axis of the wire.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now the drawings, and more particularly to FIGS. 1 and 2, the present invention is for an orthodontic arch wire which is generally designated by the reference numeral 10. The arch wire 10 is elongate and defines an axis of symmetry which passes through the central region of the wire. The advantages of the present arch wire, which will be more fully described hereafter,

are made possible by the specific construction. The arch wire is made from a single strand having a circular cross-section having a diameter t. The strand is configurated into a tightly wound helix having successively abutting looped turns 12 of generally circular crosssection. Each turn 12 of the helix defines a plane which is normally substantially parallel to the other respective planes defined by the other turns when the arch wire extends along a straight line. According to one presently preferred embodiment, the parallel planes defined by the turns are substantially perpendicular to the axis of the arch wire this being shown in FIG. 1.

The arch wire, shown in FIGS. 1 and 2, is configurated into a helix and has looped turns 12 each with a common internal diameter d which is equal to or less than twice the diameter or thickness t of the individual strand from which the orthodontic arch wire 10 is made as measured in the radial direction of the helix. The outer dimension D of the arch wire 10 is in the range of dimensions commonly used for arch wires solid or otherwise. The orthodontic arch wire 10 is constituted of a single metallic strand, preferably stainless steel, which is relatively flexible in nature.

The internal dimension d is advantageously made as small as practical in order to provide the required stiffness of the wire over long lengths. The opening in each of the turns has an internal dimension d and together forma passage or lumen 18 through the arch wire 10. The passage is normally created during the formation of the helix. Thus, one way of manufacturing the arch wire in accordance with the present invention comprises the step of configurating a wire into a tightly wound helix about a mandrel 60 (shown in FIG. 3), which may or may not be left in the arch wire subsequent to the manufacture thereof. Slightly modified characteristics of the arch wire 10, which may be desirable in certain cases, may be obtained by leaving the mandrel 60 in the lumen of the arch wire.

Because of the tight abutting relationship of each of the looped turns 12 to each other, the resultant arch wire 10 is provided with an enhanced degree of stiffness a degree of stiffness which is greater than that of an openly wound helix made from a similar strand. Thus, whereas an open helix or coil would have substantial flexibility over longer lengths of the arch wire, the subject arch wire 10 has a stiffness which almost equals that of a solid wire of equivalent cross-sectional area. This arises partly from the support which adjacent turns offer to one another. Of course, because of the looped configuration, the arch wire 10 is somewhat more flexible and less stiff than its solid wire counterpart over long lengths. The stiffness is also greatly enhanced by minimizing the diameter of the inner passage or lumen 18 of the wire 10. Selecting the lumen or passage diameter to be a dimension not greater than twice the diameter of the coil strand has been found to provide satisfactory results. Also, arch wire 10, pursuant to the subject embodiment, may sustain great compressive forces in directions longitudinal of the axis of the arch'wire without deforming the arch wire or loop turn configuration.

Orthodontic procedures usually incorporate the utilization of an orthodontic bracket, shown in FIG. 3, generally denoted by the reference character 22. The bracket 22 is mounted on a band 24, only a fragment of the band being illustrated in FIG. 3. The band is generally annular-like and is configurated to be tightly titted and mounted upon a respective tooth (not shown). Brackets are sometimes directly mounted on a tooth by bonding the bracket to the tooth with cement. The bracket 22 has a base portion 28 and a flanged portion 30. The flanged portion 30 is provided with a pair of oppositely directed lips 32 which overlie in spaced relationship the base portion 28 of the bracket 22. Moreover, the bracket is provided with, between the opposite lips 32, a centrally disposed generally U-shaped wire guide-channel 34. An orthodontic arch wire, such as wire 10, is receivable into the guide-channel 34. A conventional ligature or fastener 36 is forced over the oppositely directed lips 32 in a conventional manner so as to be detachably associated with the flanged portion 30 to thereby tightly secure the orthodontic arch wire 10 within the guide channel 34.

Normally, a plurality of orthodontic brackets are mounted on respective teeth and, thereafter, are interconnected to one another through the intermediary of an orthodontic arch wire 10 in a manner generally examplified in FIG. 5. In FIG. 5, however, there is omitted from the illustration the fastener 36 illustrated in FIG. 3. The reason for omitting the fastener from FIG. 5 is to permit illustration of the manner by which the orthodontic arch wire 10 pursuant to the first described embodiment illustrated in FIGS. 1 and 2 permits localized control over the directional movement of a maloccluded tooth. When the arch wire 10 is appropriately mounted and constrained within the guide channel 34 of each of the orthodontic brackets 22, the arch wire may be longitudinally tightened so as to cause movement of the maloccluded teeth in directions generally longitudinally of the wire 10. The arch wire 10 pursuant to the present invention, when mounted within the appropriate guide channels 34 of each of the orthodontic brackets 22 respectively, may be flexed or bent slightly or significantly. At such time, the loop turns 12 originally abutting against one another prior to being mounted within the orthodontic brackets 22 will resiliently flex at localized positions on either side of the guide channel 34 of each of the brackets 22. Although slight bending is shown in FIG. 5, the wire 10 can be bent significantly without permanently being deformed and loosing its resiliency. Thus, the wire 10 pro vides an improved working range over that provided by solid wires. During this process, adjacent turns slightly or at least partially separate from one another in a manner illustrated in FIG. 5. Those turns which experience this partial separation, are generally designated by the refernece characger 12' in FIG. 5.

The slight separation of the originally abutting looped turns 12' of the arch wire 10 permits localized control over the vertical alignment of a particular tooth since the turns 12' as slightly separated from one another tend to elastically return to an abutting orientation thereby causing a maloccluded tooth to properly align itself vertically. The increased working range of the arch wire 10 insures that the arch wire retains its resiliency despite substantial flexing thereof.

Accordingly, the single metallic strand from which the orthodontic arch wire 10 is formed overcomes the disadvantages typically associated with single strands of solid wire which are not helically coiled in a manner pursuant to the prspresent invention. With the conventional wires, as described in the BACKGROUND OF THE INVENTION, these do not provide the requisite working range over small lengths in the range of 2 to 4 millimeters. However, by imparting a tightly-wound helical configuration as above described, bending of the arch wire 10 is possible to a greater extent without permanently deforming the wire. It has been found that a wire having the above described helical construction provides increased flexibility as well as increased working range in small spaces this being particularly suitable for orthodontic work.

The single strand coil pursuant to the present invention overcomes the deficiencies of multi-strand arch wires in several respects. Firstly, the subject arch wire 10 is usually more flexible than the multi-strand arch wire since the flexibility of the present arch wire is limited only by a single strand while in the multiple arch wire configurations the overall flexibility is a function of the combined flexibility of all of the individual strands. Additionally, the subject arch wire can be made to resist abrasive objects in the mouth better than the multi-strand arch wire by making the single strand in the present inventin have a dimension greater than that of the individual strands in the multi-strand arch wire configuration without compromising working range over short lengths. Also, by making the single strand of the subject wire somewhat greater in crosssectional area than the cross-sectional areas of the individual strands of the multi-strand arch wire, the danger of breakage and subsequent piercing and mutilation of the sensitive tissues in the mouth are similarly decreased or eliminated.

Optionally, a soft coating 50 may be placed about the exterior of the arch wire 10 this being illustrated in Flg. 4. Advantageously, the coating can be made from a flexible plasticized or elastic elastomeric material which can simultaneously serve to protect the tissues in the mouth from the wire as well as to prevent food particles from entering into the spaces in the wire where they may decay and present problems to the wearer of the arch. The coating 50, being plasticized and elastic, does not substantially effect the flexibility or working range of the arch wire 10.

Although the above embodiment was described in terms of an arch wire of circular cross-section which makes up the helix or arch wire, any other suitable cross-section of the arch wire or configuration of the looped turns 12 may be utilized. Thus, the loopsed turns 12 have been shown to be circular, although oval or rectangular turns may be utilized. In FIGS. 6 and 7, turns 16 are shown which similarly successively abut against each other the turns being made from a strand of square or rectangular cross-section. As with the first configuration illustrated in FIGS. 1 and 2, the common internal dimension d of the lumen is made equal to or less than twice the thickness 1 of the strand from which the orthodontic arch wire 14 is made. As before, the orthodontic arch wire 14 is constituted of a single preferably metallic strand such as stainless steel which is flexible in nature and coiled into a square coil such that each of the looped turns 16 of the wire 14 abuts against adjacent turns and are positioned in respective planes which are substantially parallel to one another. Also, each of the turns 16 defines a plane which is substantially normal to the axis of the elongated arch wire 14. The wire 14 functions in the same manner as does the arch wire 10 and exhibits similar properties over the long and short lengths as described above.

In connection with both the arch wires 10 and 14, the turns have up to now been described as defining planes which are substantially normal to the axis of the respective arch wires. A slight modification of both of these embodiments is shown in FIG. 8 wherein each of the turns, circular or rectangular, each define a plane which is oblique to the axis of the respective arch wires. This modification prevents the fastening wires 36 from entering between and separating the adjacent turns since these fastening wires are also generally in planes which are substantially normal to the axis of the arch wires.

One method of manufacturing the arch wires in accordance with the present invention comprises the step of winding the individual strand about a mandrel 60, shown in FIG. 3. As suggested above, the mandrel may either be left inside the arch wire or removed therefrom prior to use the characteristics being slightly affected when it is left inside the arch wire and may prove desirable under certain circumstances. However, where most of the work involves longer lengths of arch wire, the mandrel is useful for providing added stiffness and permits the formation of arches as well as loops and U-shapes by deforming the arch wire and the mandrel simultaneously. On theother hand, where most of the work involves bends in small spaces, the mandrel 60 is advantageously removed so as -to increase the working range of the arch wire. It should be noted that loops and U-shapes can similarly be made with this subject arch wire as were made up to now with conventional wires.

Numerous alternations of the structure herein disclosed will suggest themselves to those skilled in the art. However, it is to be understood that the present disclosure relates to a preferred embodiment of the invention which is for purposes of illustration only and is not to be construed as a limitation of the invention.

What is claimed is:

l. A method of applying an orthodontic arch wire to an orthodontic bracket on a maloccluded tooth, the orthodontic bracket generally having a U-shaped channel terminating in a pair of opposite ends, said method comprising the steps of coiling a single flexible strand into a helix having a lumen extending therethrough and forming an array of successively abutting, substantially parallel turns, said strand when formed into said turns having a predetermined radial thickness and said turns having a common internal dimension of said lumen so greater than twice said predetermined radial thickness of said strand; inserting the twisted strand into the U- shaped channel of the orthodontic bracket; bending the coiled strand where desired such that looped-turns at each of the opposite ends of the U-shaped channel are at least partially moved out of contact with one another; and securing the coiled strand within the U- shaped channel. 

1. A method of applying an orthodontic arch wire to an orthodontic bracket on a maloccluded tooth, the orthodontic bracket generally having a U-shaped channel terminating in a pair of opposite ends, said method comprising the steps of coiling a single flexible strand into a helix having a lumen extending therethrough and forming an array of successively abutting, substantially parallel turns, said strand when formed into said turns having a predetermined radial thickness and said turns having a common internal dimension oF said lumen so greater than twice said predetermined radial thickenss of said strand; inserting the twisted strand into the U-shaped channel of the orthodontic bracket; bending the coiled strand where desired such that looped-turns at each of the opposite ends of the U-shaped channel are at least partially moved out of contact with one another; and securing the coiled strand within the U-shaped channel. 